Photorefractive keratectomy (PRK) is a type of laser eye surgery that permanently changes the shape of the cornea, improving the way it focuses light on the retina. Before LASIK, PRK was the most commonly used form of refractive surgery, and although the two procedures share some similarities, each is performed differently and has its own distinct set of advantages and disadvantages.
Like LASIK, PRK is used to correct myopia, hyperopia and astigmatism by reshaping the cornea. However, one of PRK's advantages is that it's used on the surface of the cornea, not underneath, as in LASIK. PRK requires no incisions, leaving the structural integrity of the cornea intact.
During PRK surgery, thin layers of the epithelium, or the outer cell layer of the cornea, are removed with cool ultraviolet beams of an excimer laser. By breaking the bonds that hold the tissue molecules together, the cornea is reshaped, correcting the refractive error. Immediately following surgery, either a patch or a bandage contact lens is placed on the eye for protection.
Patients may have some discomfort for the first few days following surgery, and vision will remain blurry anywhere from three days to a week. It often takes a month or longer to achieve best vision, and eye drops may also be required for an extended period. The extended recovery time for PRK versus LASIK is often cited as one of the procedures greatest disadvantages.
Possible complications of PRK surgery include undercorrection, overcorrection, poor night vision and corneal scarring. Permanent vision loss is very rare. In studies monitored by the FDA, 95% of eyes were corrected to 20/40, the legal limit for driving without corrective lenses in most states.
PRK still remains the preferred method of refractive eye surgery for patients with thin corneas and large pupils. It is also highly effective in treating extreme near-sightedness and may offer an alternative to those who are otherwise not good candidates for LASIK. Candidates for PRK must have a stable and appropriate refractive error; be free of eye disease; at least eighteen years old; and willing to accept the potential risks, complications and side effects of PRK.
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